OFFSET
1,2
COMMENTS
Equals triangle A177990 * [1,2,3,...]. - Gary W. Adamson, May 16 2010
LINKS
Girtrude Hamm, Classification of lattice triangles by their two smallest widths, arXiv:2304.03007 [math.CO], 2023.
Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).
FORMULA
From R. J. Mathar, Feb 22 2009: (Start)
a(n) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5).
G.f.: x*(-1-x-x^2+x^3)/ ((1+x)^2*(x-1)^3). (End)
a(n) = Sum_{k=1..n} k^(k mod 2). - Wesley Ivan Hurt, Nov 20 2021
MATHEMATICA
a = {}; r = 1; s = 0; Do[k = 0; Do[k = k + (Sin[Pi m/2]^2) m^r + (Cos[Pi m/2]^2) m^s, {m, 1, n}]; AppendTo[a, k], {n, 1, 100}]; a
CROSSREFS
Cf. A177990. - Gary W. Adamson, May 16 2010
KEYWORD
nonn,easy
AUTHOR
Artur Jasinski, May 12 2008
STATUS
approved